Project Summary For the immense undertaking by many malaria-endemic nations to eliminate malaria, interruption of malaria transmission has been recognized as one of the greatest challenges, which requires integrated approaches. Plasmodium vivax, the most geographically widespread human malaria, is more resilient to conventional malaria control measures due to its intrinsic biology such as hypnozoite formation responsible for relapses and earlier gametocyte development enabling transmission before manifestation of symptoms. Transmission- blocking vaccines (TBVs) are a promising strategy especially suited for the task of elimination of vivax malaria. However, the progress in TBV development has been very slow, whereas TBV research for P. vivax lags even far behind that for Plasmodium falciparum. With only five parasite antigens as the top TBV candidates, concerted efforts to identify new TBV antigens are urgently needed. In this application, we propose to use an innovative antigen discovery pathway taking advantage of new protein expression and immunoscreening technologies, and advancement in vaccine design and delivery platforms. We aim to 1) discover new sexual- stage antigens by in silico prediction and immunoscreening, and evaluate their transmission reducing activities in Plasmodium berghei; 2) evaluate a TBV combination strategy targeting both pre- and post-fertilization antigens; and 3) assess the transmission reducing activities of new TBV candidates for P. vivax using transgenic P. berghei and clinical P. vivax isolates. Results from these comprehensive studies will contribute to a better understanding of sexual development in malaria parasites and identification of new sexual-stage antigens for the TBV development pipeline.